Crystal structure and properties of U2Co3Al9

A new ternary compound with stoichiometry U2Co3Al9 has been synthesized. It adopts the orthorhombic Y2Co3Ga9-type structure (space group Cmcm, Z = 4, a = 12.824(2) Å, b = 7.515(1) Å, c = 9.249(2) Å). Measurements of dc- and ac-magnetic susceptibility, electrical resistivity, and magnetoresistivity on polycrystalline samples have been performed. The Curie–Weiss law is strictly followed, with θCW = −48 K and μeff = 3.2 μB. A small kink observed in the temperature dependence of the resistivity is attributed to a phase transition at Tt = 8 K. The magnetoresistivity was found to be negative at all temperatures examined below 45 K, with a sharp minimum at Tt = 8 K.